DescriptionAn analytical model to calculate the noise spectral density in Metal-Semiconductor-Metal (M-S-M) structure of Schottky contacts has been developed. The model based on the linearization of Langevin approach of carrier motion inside a bulk semiconductor, and taking into account the fluctuations in the leakage current through the structure due to the barrier lowering by the image force effect. Particularly, the calculations describe two quantities of noise: electric field and total current spectral densities. The results obtained from the Au-CdTe-Au Schottky structure exhibit sharp resonances due to the effect of plasma frequency oscillations and the relative thickness of the depletion region below the anode. Moreover, the noise current spectrum exhibits Lorentzian behavior when the M-S-M has the form of a homogenous structure (thickness of depletion region ≈ 0). These results are in agreement with that reported by Monte Carlo technique of metal Schottky structure. The discussion of the noise spectra as a function of structure parameters revealed that the nanometric M-S-M structures with undoped CdTe can be used as Schottky detectors/emitters in Terahertz frequency applications.

DescriptionWe present experimental data showing that the equiatomic CrMnFeCoNi high-entropy alloy undergoes two magnetic transformations at temperatures below 100 K while maintaining its fcc structure down to 3 K. The first transition, paramagnetic to spin glass, was detected at 93 K and the second transition of the ferromagnetic type occurred at 38 K. Field-assisted cooling below 38 K resulted in a systematic vertical shift of the hysteresis curves. Strength and direction of the associated magnetization bias was proportional to the strength and direction of the cooling field and shows a linear dependence with a slope of 0.006 +/- 0.001 emu/T. The local magnetic moments of individual atoms in the CrMnFeCoNi quinary fcc random solid solution were investigated by ab initio (electronic density functional theory) calculations. Results of the numerical analysis suggest that, irrespective of the initial configuration of local magnetic moments, the magnetic moments associated with Cr atoms align antiferromagnetically with respect to a cumulative magnetic moment of their first coordination shell. The ab initio calculations further showed that the magnetic moments of Fe and Mn atoms remain strong (between 1.5 and 2 Bohr magneton), while the local moments of Ni atoms effectively vanish. These results indicate that interactions of Mn- and/or Fe-located moments with the surrounding magnetic structure account for the observed macroscopic magnetization bias.